According to followup on IRC, Gitter's compose mode makes Enter insert a newline, and you need to use Ctrl-Enter instead to send the message.
Most terminals do not support Ctrl-Enter (it just sends an Enter). However, many do support Alt-Enter. Right now, Alt-Enter also inserts a newline. It may make sense to swap Enter and Alt-Enter in "compose mode".
Re the name, "multiline mode" makes more sense for a shell, so I changed the title.
Implementing this request might be warranted but since it is trivial to drop into an external editor for complicated edits is it worth the cost to implement this feature? See, for example, https://github.com/elves/elvish/issues/636#issuecomment-619315679 and https://github.com/elves/elvish/issues/535#issuecomment-615963855. It seems to me that a change that makes it easy to edit a command in an external editor is more useful and would resolve this request; albeit in an unexpected manner.
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According to followup on IRC, Gitter's compose mode makes Enter insert a newline, and you need to use Ctrl-Enter instead to send the message.
Most terminals do not support Ctrl-Enter (it just sends an Enter). However, many do support Alt-Enter. Right now, Alt-Enter also inserts a newline. It may make sense to swap Enter and Alt-Enter in "compose mode".
Re the name, "multiline mode" makes more sense for a shell, so I changed the title.